Archean Banded Iron Cabochons

November 2, 2009

I recently bought a vintage lapidary machine on Craigslist.  It’s for cutting cabochons, and includes a trim saw, grinding wheels, sanding drum, and buffing wheel.  I mostly want it for making beads and cutting preforms for gem carving. 

Wyoming Archean Banded Iron Cabochons

Wyoming Archean Banded Iron

Double-sided drilled and polished pendant, 31x21x5mm.

Matched pair of triangular cabochons, 20x16x4mm.

This is Early Archean banded iron from the Shirley Basin in southeastern Wyoming.  At 3.7 billion years old, it is one of the oldest rocks on earth.  This rare material is similar in composition to Australian “tiger iron” but is not as colorful and is almost never cut as a gem.   The polished stones were cut from two pebbles that I collected ten years ago.   The gray metallic stripes are mostly hematite with minor black magnetite layers.  The brown layers are composed of tiny interlocking  sheaves of crocidolite crystals, an iron-rich metamorphic silicate that forms at relatively high temperature and pressure. 

The larger stone will adorn a medicine bag.  I will probably set the triangular pair as earrings.

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One Response to “Archean Banded Iron Cabochons”

  1. I like Tiger Iron–bought some round beads of it and used it in a couple of necklaces–I much prefer it to Tigereye which has too much gold in it for me.

    These are VERY nice. I tend to like stones that aren’t conventionally pretty–more challenging to do something interesting with them, don’t you think?

    That’s great you found your own machine!

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